Even though cardiogenesis and changes in hemodynamic characteristics during the early development of the chick are well documented, the literature regarding the dependence of the cardiac contractility on oxygen availability is relatively scarce . During the first week of development of the chick, despite its structural simplicity, the general functional organization of the embryonic heart is similar to that of the mature heart, and the physiological PO2 values found in the intraembryonic tissue and blood vessels are rather low, ranging from nearly 0 to 8 kPa .In the three- to six-day-old embryo a moderate hypoxia of 6 kPa elicits tachycardia, severe hypoxia produces bradycardia, arrhythmia or asystole =, and inhibition of the oxidative phosphorylation induces cessation of spontaneous contractile activity within less than 30 mins . In the older chick embryo (seven to 19 days) exposure to hypoxia alters cell membrane function and results in bradycardia and arrhythmia . In these experiments, however, the actual PO2 at the level of the myocardial tissue was not precisely controlled, and rapid anoxia-reoxygenation transitions were not possible. Preliminary reports of this work have appeared as abstracts. Your drugs could be so cheap – get allergy relief at trusted foreign online pharmacy.